Recently, in industrial fields, robot apparatuses are being used widely to perform work more accurately and more quickly. Some robot apparatuses are made of a multi-link structure in which multiple links are joined to each other by multiple joint units, and by controlling rotational driving in the multiple joint units, the driving of the robot apparatus as a whole is controlled.
Here, position control and force control are known as control methods of the robot apparatus and each of the joint units. In position control, for example, a command value such as an angle is provided to an actuator of a joint unit, and driving of the joint unit is controlled according to the command value. Meanwhile, in force control, a target value of force applied to a task target by a whole robot apparatus is given, and driving of a joint unit (for example, torque generated by the joint unit) is controlled such that the force indicated by the target value is implemented.
Generally, most robot apparatuses are driven by position control since it is convenient to control and a system configuration is simple. However, position control is commonly called “hard control” since cannot easily deal with external force flexibly, and position control is not suitable for a robot apparatus performing a task (purpose of motion) while performing physical interaction (for example, physical interaction with a person) with various external worlds. Meanwhile, force control has a complicated system configuration, but can implement “soft control” of a power order, and thus force control is a control method suitable, particularly, for a robot apparatus performing physical interaction with a person and a control method having excellent usability.
For example, with regard to an example of a robot apparatus applying force control, Patent Literature 1 discloses a robot apparatus that includes a movement mechanism configured with 2 wheels and an arm unit configured with a plurality of joint units, and performs control such that the wheels and the joint units are driven in a cooperative manner as a whole (performs whole body cooperative control).
In addition, with force control, there is demand to detect more accurately the torque in each joint unit of the robot apparatus (including the generated torque generated by the joint unit and the external torque imparted to the joint unit externally), and perform feedback control and/or feed-forward control. For example, Patent Literature 2 discloses a torque sensor that, by including a split structure (decoupled structure), realize accurate torque detection with the influence of vibration decreased as much as possible.
Also, Patent Literature 3 below describes a technology that uses a surgical microscope adopting a structure with a balanced center of gravity to thereby enable operation with a light operating force.